Since the development and use of cis-platin as an effective anti-tumor agent, extensive research has been directed towards finding platinum complexes which might demonstrate similar or better antitumor activity while providing improvements in other properties, e.g., reduced toxicity or other undesired side effects.
A variety of cis-platin analogs have been extensively investigated, including complexes of Pt(IV) such as cis-trans-cis-PtCl.sub.2 (OH).sub.2 (i-prNH.sub.2).sub.2 (U.S. Pat. No. 4,394,319) and PtCl.sub.4 (DACH) (U.S. Pat. No. 4,550,187). Most Pt antitumor compounds described to date are hydrophilic in that they dissolve more readily in water than they do in common organic solvents, e.g., acetone, methylene chloride, etc. Examples of such hydrophilic complexes include cis-platin itself and carboplatin. Recently, a variety of liposoluble Pt complexes have been reported (e.g., bis(caprato)DACH Pt) that are poorly soluble in water but readily dissolved in organic solvents. See Maeda et al., JPN, J. Cancer Res. 77, 523-525 (1986).
Certain 1-amino-2-aminomethylcyclopentane platinum (II) and (IV) complexes have also been described in U.S. Pat. No. 4,466,924. This patent refers generally to the possibility of including acetate, oxalate, malonate or carboxylate substituents attached to the Pt atom. However, no specific examples of such complexes are given in the patent.